A typical integrated circuit structure is made up of dies that include active devices such as transistors and capacitors. These devices are initially isolated from each other, and interconnect structures are later formed over the active devices to create functional circuits. On top of the interconnect structures, metal pads are formed and exposed on the surface of the respective die. Electrical connections are made through the metal pads to connect the die to a package substrate or another die.
In an aspect of conventional packaging technologies, such as fan-out packaging, redistribution layers (RDLs) may be formed over a die and electrically connected to the metal pads. Input/output (I/O) pads such as solder balls may then be formed to electrically connect to the metal pads through the RDLs. An advantageous feature of this packaging technology is the possibility of forming fan-out packages, which means the I/O pads on a die can be redistributed to a greater area than the die, and hence the number of I/O pads packed on the surfaces of the dies can be increased.